Production of light by electricity



June 4, 1929. E. PODSZUS I PRODUCTION OF LIGHT BY ELECTRICITY Jiz' i -HHHHHHHHHHH= Patented 1......4, 1929.

UNITED STATES 1,715,783 PATENT OFFICE.

EMIL PODSZUS, OF FRIEDRICHSHAGEN-BERLIN, GERMANY, ASSIGNOB TO SIEMENS & 'HALSKE AKTIENGESELLSGKAFT, OF SIEMENSSTLADT, NEAR BERLIN, GERMANY,

A CORPORATION OF GERMANY.

PRODUCTION LIGHT BY ELECTRICITY.

- Application filed September 2, 1921, Serial No. 498,173, and in Germany July 26, 1918.

My invention refers to the production of light by electricity and more'especially to lighting devices producing light'by the passage of the electric current through vapours capable, on bein raised to a sufiicientlyhigh temperature, 0 emitting luminous rays, such as metal vapours and more especially mercury vapour or the vapours of metal compounds suchas compounds of the earth alkalies or the rare earths.

The particular eflect ofthe so-called flame arc lamps is based mainly on the luminosity of such vapour s'heated by the electric current. However the practical eflects 0b current,

tained with such lamps remain far below the theoretical maximum.-

I have ascertained in the course of extensive investigationa'thatin order to improve the eihci'ency ofsuch lamps, it is important to raise the intensityof the current and the current density in that part of the incandescent vapor which conducts the current, up to a certain amount.

I have further ascertained that the mini mum amount towhich the density must be raised depends upon the strength of the inasmuch as strength of current in ampefes and of the current density in amperes per square millimeter should be at least 50. In consequence thereof, assuming" the strength of current to be amperes, the-current density "should be equal to at least 1 ampere per square "millimeter of the sectional area of the vapour column effectively conducting the current.

In order to. obtain such a high currentdensity and at the same time to restrain as far as possible the detrimental absorption of light in the'cooler layers of the vapour, it is imperative, instead of'allowing the vapour to spread freely, as hah been the. case hitherto, to concentrate it within a tubular sleeve arid to conductit therein at least for that portion of'its path where the productionof light takes place. This sleeve should be'so dimensioned that the sectional area of the vapour column enclosed therein answers the condition mentioned above insofar as the sectional area in square millimeters does not exceed the fiftieth part of the square of the strength of. current in amperes. 'Care should be taken at the same time to make the product ofarc this-field is very the sleeve long enough, the whole arrangement being such that the vapour column within the sheel is utilized as perfectly as possible for the conduction of the current.

'One may as well employ a magnetic guide or enclosure, masses of iron and current carrying conductors they being arranged v in such a manner that the lines of current are crowded together on a narrow space.

In the drawings affixed to this specification and forming a part thereof an arc lamp in accordance with the present invention is illustrated,

Fig. 1 is a diagrammatic longitudinal section, and

L Fig. 2 is a similar section'of a modification, the non-essential parts being broken away and being assumed for the present purpose to be substantially similar to those.

shown in Fig. 1. v

Referrin to Fig. 1' of the drawings, a: is the electro e generating the vapour column and b is a coil enclosing that part of the electrode which is nearest to the are, an insulating sleeve 11 being insertedbetween them. 0 is a tubular iron core dimensioned in accordance with the size of the arc in such a manner that the path of the arc is closely surrounded by a powerful parallel magnetic field in tubular fashion, whilewithih the weak. The opposite electrode 65 is provi ed with a current carrying coil 6, wound in such adirection that the magnetic polarity of its end facing the arc is oppositeto that existing atthe are end of'coil b of the other electrode. By these means an effective counter pole for the tubular Hnagnetic field is formed. 2, 2 are rings for'feeding the electrodes with cur rent, 3 is a sourceof electricity furnishlng it s-turn a pair of worm wheels 8, 8 disposed above and below the. rear end of electrodea on axles 9, 9 crossing each other at a pointed angle and carrying friction rollers 10, 1 0

in. frictional contact with theelectrode.

Owing to the worm wheels 8, 8 bein disposed on the same side of the worm s aft F? the rollers 10, 10 revolve in the same direction and, cause the electrode a to turn .vancing same.

around its axis. Owing to the roller axles 9 being disposed at an angle to each other the rollers at the same time impart to the electrode a slow advancing motion.

12 is a shaft revolved by worm gear 6 and 13 is a roller on said shaft in frictional contact with the counter electrode at and ad- 24 is a tubular element within which one of the electrodes, in this case 23, is disposed. This, sleeve which does not partake in the conduction of current may consist, as shown in Fig. 1, of refractory non-conducting material. Furthermore, while operating in Fig. 1 in conjunction with the magnetic means for closely confining the are, this sleeve in some instances may form itself al-' ready a sufficientlyeifective means for that purpose without making use of the magnetic means, for instance in Fig. 1 without exciting the magnet coil 6.

Incorder to obtain the highest possible intrinsicbrilliancy the concentration of the luminous vapour should be chosen as high as possible and therefore all diluting gases j and vapours having an unfavorable emission, such as carbon vapour, should be kept away from the zone of incandescence. One

' should avoid; employing carbon electrodes underconditions, fostering the generation of any appreciable quantities of carbon vapour which might be introduced into the zone of incandescence. In case the tube 24 is made of conducting material, as shown for instance in Fi 2, I have found carbon to be very satis actory. By suitable means, described below, such a carbon tube is pre vented from emitting carbon vapours, so, that the incandescent zone'is kept free from such vapours.

In all those cases where it is of importance to protect the sleeve against the effects of the very high temperature I prefer employing a special cooler which may be a water jacket such as shown in Figs. 1 and 2 of-thedrawin s where 14 is the cooler consistin b b of a jacket preferably made of copper or another metal of superior heat-conductivity,

fed "with water and insulated from, but closely surrounding the sleeve. This jacket should'conduct the water close up to the mouth of the sleeve and the water feed should be controlled in such a manner that the great quantities of heat evolved are earried away before steam ca n;form.-""

- The vapour used may eitherbe introduced into the sleeve in'any suitable manner or it may be generated therein. I-may for instance introduce mercury vapor into the sleeve from the rear as. shown in Fig. 2, where a is'the electrode, o is the sleeve and w is the mercury inlet.-- In general the vapour contained within the sleeve will slowly escape therefrom whenthelamp is working and it is therefore necessary to replace the lost quantity of vapour. This can be effected by suitably introducing a uniform jet of vapour through pipe 00.

\Vith the arrangements described above an exceedingly high light efliciency approaching very nearly the theoretic maximum can be obtained. At the same time there results an extraordinary increase of light intensity per unit of area of the source of light. These advantages are of the great-, est importance in search lights and an almost point source of light is obtained even with very high currents.

I claim:

1. In an electric lighting device in combination, a pair of solid electrodes, means for forming an electric are between said electrodes, means for producing light emitting vapours for feeding the are formed between said solid electrodes and a rigid cooling-device for restricting the cross section of at least a portion of the arc vapour column to approximately the'cross section of one of the electrodes to "prevent its spreading for the purpose set'for'th. I 90 2. In an electric lighting device in combi nation, a pair of solid electrodes, means for forming an electric are between said electrodes, means for producing light emitting vapours for feeding the are formed between said solid electrodes and a tubular sleeve around a part'of the vapour column formed between said electrodes, said sleeve having an inner diameter approximately equal to that of one of the electrodes.

3. In an electric lighting device in combi nation, a pair of solid. electrodes, means for forming an electric are between said electrodes, means for producing light emitting vapours for feeding the are formed between 105 said solid electrodes and a highly refractory tube'placed around .a part of the vapour column formed betweensaid electrodes, said tube having an inner diameter approximately equal to the diameter of one of the electrodes.

4,. In an electric lighting device in combination, a pair 'of solid electrodes, means for forming an electric are between said electrodes, means for producing light emitting vapours for. feeding the are formed between said solid electrodes and a carbon tube around a part of the vapour column formed between said electrodes.

5. In an electric lighting device in combination, a pair of solid-electrodes, means for forming an electric are between said electrodes, means for producing light emitting vapours for feeding the arc formed between said solid electrodes, an enclosure around a part of the vapour column formed between said electrodes for restricting the cross section of said column substantially to that of one of the electrodes and ineans for cooling said enclosures 6. In an electric lighting device in combi nation, a pair of solid electrodes, means for forming an electric arc between said electrodes, means for said solid electrodes and a tubular sleeve around a part of the vapour column formed producing light emitting 5 vapours for feeding the are formed between between said clectrodes said sleeve having an inner diameter substantially equal tothat of one of the electrodes and means for cool- 1 ing said tubular sleeve.

In testimony whereof I aflix my signature.

EMIL PoDszus. 

